Retinopathy. This eye problem occurs in 75% to 95% of adults who have had diabetes for more than 15 years. Diabetic retinopathy in type 1 diabetes is extremely rare before puberty no matter how long they have had the disease. Medical conditions such as good control of sugars, management of high blood pressure, and regulation of blood fats like cholesterol and triglycerides are important to prevent retinopathy. Fortunately, the vision loss isn't significant in most people with the condition. (page 2)
Kidney damage. About 35% to 45% of people with type 1 diabetes develop kidney damage, a condition called nephropathy. The risk for kidney disease increases over time and becomes evident 15 to 25 years after the onset of the disease. This complication carries significant risk of serious illness -- such as kidney failure and heart disease. (Page 2)
Poor blood circulation. Damage to nerves and hardening of the arteries leads to decreased sensation and poor blood circulation in the feet. This can lead to increased risk of injury and decreased ability to heal open sores and wounds, which in turn significantly raises the risk of amputation. Damage to nerves may also lead to digestive problems such as nausea, vomiting, and diarrhea. (Page 2)
Seibel, John A. "Type 1 Diabetes." WebMed. N.p., 8 Mar. 2009. Web. 8 Nov. 2010. <http://diabetes.webmd.com/guide/type-1-diabetes?page=2>.